Runners are commonly used when warehousing, shipping and packaging large, bulky items such as appliances. Due to the weight and/or size of these items, they can be difficult to move. In warehousing situations, the ability to slide these items into and out of packaging is desired to aid both in packing and un-packing of the bulky item. The advantages in unpacking are further provided in that installation is aided due to the ability of the runner to easily slide along a floor and make it easier to move the bulky item closer to the installation position.
Runners mounted to the bottom of appliances also provide protection to the corners and edges of the appliance in that the runners extend beyond the bottom perimeter of the appliance and provide a bumper that prevents the corners from becoming dented and scratched during packaging, shipping and warehousing.
Many runners currently available are made with blow molding, which provides an inexpensive way of manufacturing a plastic runner without the material costs of injection molding a solid runner. The difficulty with currently available blow molded runners is that stiffness of the runner is often inadequate in the warehousing scenario when multiple bulky items, such as dishwashers are stacked on top of each other. The weight of the stack of bulky items is concentrated on the runners, which are often made of primarily a double walled configuration.
Although double walled configurations add bending stiffness over longer lengths, the thickness and/or configuration of the walls may provide insufficient localized stiffness. The bulky item is often positioned on the runner at specific points, which results in point like loads or loads that are distributed over a relatively small portion of the runner.
In this case, the prior art double wall configuration of the mounting areas allows for the mounting areas to buckle under load despite the fact that the overall bending stiffness of the runner is sufficient for supporting the overall weight of the bulky item. In addition, the cross section may have a tendency to deform or bend away from the axis of the force. See FIG. 9 for an example showing one possible localized deflection of a runner (movement from A to B).
The buckling and deformation problems around the mounting areas can create a situation in which the entire stack can shift and if the buckling is too much, there is the possibility that an appliance becomes damaged. For example, imagine the stack shown in FIG. 2 used the runner of FIG. 9 instead of the improved runner disclosed herein.
Therefore, it is desired to provide an improved runner for bulky and heavy items such as appliances so that the runner has both increased localized stiffness at the attachment points for the appliance and sufficient overall stiffness to resist deflection under load.